Historically, complete removal of a disc from between adjacent vertebrae resulted in the need to immovably fuse the adjacent vertebrae together, and this “spinal fusion” procedures is still used today as a widely-accepted surgical treatment for disc removal stemming from, for example, a degenerative disc disease or disc injury. However, in many instances, disc arthoplasty—the insertion of an artificial intervertebral disc into the intervertebral space between adjacent vertebrae—may be preferable to spinal fusion as the former may help preserve some limited universal movement of the adjacent vertebrae with respect to each other whereas the latter does not. As such, the objective of total disc replacement is not only to diminish pain caused by a degenerated disc, but also to restore anatomy (disc height) and maintain mobility in the functional spinal unit so that the spine remains in an adapted “sagittal balance” (the alignment equilibrium of the trunk, legs, and pelvis necessary to maintain the damping effect of the spine).
Several forms of intervertebral implants include an upper part mounted to an adjacent vertebra, a lower part mounted to another adjacent vertebra, and a rotation-assist insert located between these two parts. In addition these intervertebral implants are often very small—perhaps ten millimeters wide and a few millimeters high—and are thus difficult for surgeons to hold, orient, and emplace when using just their fingers. Nevertheless, implantation of these intervertebral devices (or “implant devices”) requires precise and careful emplacement in order to ensure correction functioning.